This invention relates to a system for providing wireless multiple remote detection systems for monitoring the occurrence of a predetermined phenomena and, more particularly to such devices which include wireless transmission and receiving devices as a part thereof.
There have been numerous suggested types of detector devices, amongst them fire or smoke detectors. Such devices typically are powered by a battery or from electrical service and are designed to sound an alarm at the sight of other detection of smoky conditions. In some prior art devices, the detectors are individually connected to a common control station. Upon the occurrence of combustion, a signal is provided at the central station to indicate the location of the detector sensing combustion. In other systems, the detectors are connected in a loop circuit with a control station. Upon one detector sensing combustion, a signal characteristic of that detector, such as a signal of a predetermined frequency, is provided over the loop to the station, so that the location of the detector generating signal may be determined by multiplexing techniques. Such systems are obviously complex.
One problem, however, for detection devices and, in particular, smoke or burglar detection devices for use in the home or in factory locations, is that once the detector becomes enabled, that the warning signals will reach the individual in a remote location. The actual location of the source of the signal is nowhere as important as knowing that a signal has been given.
One suggested device was proposed by Martin et al. in U.S. Pat. No. 4,160,245. Martin et al. proposes a transmitted signal which may be received by a plurality of local receivers. The signal is transmitted by a wireless signal and the local units sound the alarm. A requirement of this system is that the receivers be within receiving distance of the sole transmitter. If the transmitted signal is weak, it may only reach one or none of the receivers, thereby defeating the purpose of the system.
Another suggested approach has been proposed by Siegel et al. in U.S. Pat. No. 4,091,363. Siegel et al. suggests a series of smoke detectors that are hard-wired together, so that a signal initiated by one will set off all other smoke detector units. However, because of the wiring arrangement, if a wire is disconnected, none of the other units will sound. In addition, it is clear that if the battery or the electrical source has been disconnected or reduced in strength in one unit, it may prevent a signal being transmitted to the other units.
Thus, the prior art units previously suggested are either complex in construction, requiring elaborate electrical circuitry or they are merely receivers or transmitters or they are so arranged that a weak signal or a malfunction may interfere with a receipt by the other receiving systems.